1. Field of the Invention
The present invention relates to a radio transmission method to be preferably applied to building up of local area network (LAN) among multiple appliances by transmitting various information by means of radio signals and a radio transmission apparatus to which the same radio transmission method is applied.
2. Description of the Related Art
Conventionally, when a local area network is built up among plural appliances like various video appliances or personal computer and their peripherals in a relatively small area such as home and office so as to transmit data handled among them, radio transmission method has been sometimes used by attaching a radio signal transmitting/reception device to respective appliances instead of connecting a signal line directly among those appliances.
By building up a local area network by radio transmission, the necessity of connecting respective appliances directly with a signal line is eliminated, thereby simplifying a system configuration.
However, if signals are transmitted from plural transmitters when a local area network is built through the plural radio transmitters, there is a possibility that a transmission error may occur. Thus, it is necessary to access-control communication among the respective transmitters in the network according to some method.
As a conventionally well known access control method in a small size radio network, there is a method of controlling communications among respective transmitters (terminal stations: nodes) in the network in a unified way with a central transmitter (central control station: route node) in a star type connection. For example, communication in the network is controlled by polling control. According to this method, the central control station in the network transmits a control signal for polling to the other nodes in the network successively so that transmission from each node is carried out in order according to the polling. By transmission processing by the polling, transmission efficiency can be improved.
Meanwhile, in a network system like such a star type connection, it is absolutely necessary for all communication stations in the network to be capable of communicating with the central control station directly by radio. Further, a communication station incapable of communicating with the central control station directly can be made to function as a terminal station (so-called hidden terminal station) by making other particular terminal station relay a control signal from the central control station to that terminal station.
However, if the number of the communication stations constituting a network is predetermined or all communication stations to be used in the network are prepared preliminarily when such a radio network is built up, identification ID inherent of this radio network or terminal ID inherent of each communication station can be determined when a transmitter for constituting each communication station is manufactured or the network is built up. In this case, the radio network may be built up relatively easily.
If a new communication station is intended to join an existing radio network, it is necessary to set up a communication network identification ID or terminal ID on that new communication station. As a result, it takes much labor and time for the setup, so that a new communication station cannot be added so easily. Further, in addition to setup of the ID on the communication station intended to join newly, the central control station for managing the network must carry out a processing for recognizing an existence of that new communication station. Thus, this is another reason that the communication station cannot be added so easily.
Accordingly, an object of the present invention is to provide a method for allowing a communication station intended to join an existing radio network newly to join it easily.
To achieve the above object, according to an aspect of the present invention, there is provided a radio transmission method for carrying out radio transmission in a radio network comprised of plural communication stations by a control from a communication station set up as a central control station, comprising the steps of: specifying a frame cycle of radio transmission signal by a control of the central control station;
setting a predetermined position in the specified frame cycle as a slot for joining the radio network newly; and if a predetermined signal is transmitted through the slot, carrying out a processing for allowing a transmission source of the signal to join the radio network.
According to this radio transmission method, if a communication station intended to join the radio network newly synchronizes with a frame cycle set up therein by the central control station and sends a predetermined signal at a slot position for newly joining in that frame cycle, the central control station recognizes that signal and executes a processing for allowing that communication station to join the network newly.
According to another aspect of the present invention, there is provided a radio transmission apparatus for carrying out radio communication with other communication stations in a radio network, comprising: a communication processing means for transmitting and receiving a radio signal; and a control means for transmitting a signal for specifying a frame cycle with the communication processing means and when reception of the specific signal is recognized at a predetermined slot position in the frame cycle, carrying out a processing for making a transmission source of the specific signal join the radio network.
According to this radio transmission apparatus, when reception of a specific signal is recognized in the predetermined slot position, a processing for making a transmission source of the specific signal join the radio network is carried out, so that the newly joining of the radio terminal into the network is carried out under a control of this radio transmission apparatus.